Dust control, as used herein, is defined as the prevention or reduction of the extent to which fine particulates become airborne or suspended in air. Dust is generated in significant quantities during the mining, handling, transportation, and storage of coal; dust is also generated during the processing, transportation, and handling of rock, green and calcined petroleum coke, mineral ores (for example iron ore), grains, limestone, gypsum, fly ash, cement clinker, and fertilizers such as potash and phosphates, among others.
Industrial sources of fugitive dust include open operations, leaks and spills, storage, disposal, transit or poor housekeeping of sundry finely divided solid particulates. The iron and steel industries are replete with examples of the above enumerated categories. Wind erosion of exposed masses of particulate matter such as coal, mine mill tailings, or fertilizer, etc., causes both air pollution and economic waste. Detrimental effects on health and cleanliness result where the fine particles are carried aloft by winds.
Hot substrates (greater than 100.degree. C.) pose a more difficult problem for controlling dust emissions than substrates at ambient temperatures. Water can be used for dust control at ambient temperatures. However, at elevated temperatures, water evaporates quickly, and loses effectiveness at controlling dust emissions.
U.S. Pat. No. 4,780,143 discloses a foamed dust control agent which suppresses dust generation from cement clinker. The foam contains an antifoaming agent which acts to inhibit foam formation in the slurried cement. U.S. Pat. No. 5,271,859 discloses a method for inhibiting dust emission from hot (250.degree. F.) solids which comprises adding to the solids an aqueous or foamed solution of a cellulose derivative compound. U.S. Pat. No. 5,302,308 discloses a method for inhibiting dust emissions from hot (&gt;120.degree. F.) substrates which comprises adding to the substrate an aqueous or foamed solution of polyethylene oxide or a polyethylene oxide derivative.
The use of organic compounds as dust control compositions on high temperature substrates is typically ineffective or has negative side effects. At high substrate temperatures, such as temperatures above about 100.degree. C., organic compositions can be subject to decomposition which may adversely affect dust control and can result in undesirable conditions such as odors, etc.
The use of silicate in combination with a dimethyl-vinylpyridine latex binding agent is disclosed in Soviet Union Patent 1,509,547. The combination is disclosed as useful in reducing dust emissions from mineral dumps, tailing dumps, power plant ash and sloping banks or roads. The combination is applied at temperatures above about 10 to 20.degree. C. Soviet Union Patent 1,116,179 discloses a dust suppressing combination of sodium silicate and acidic tar from raw benzene rectification. The combination is employed to suppress dust in mining of mineral ores. Soviet Union Patent 1,086,184 discloses a dust control combination of sodium silicate and a copolymer of methacrylic acid and methacrylamide as a binding agent. The use of a combination of gossypol resin modified with sodium silicate and sulfite yeast liquor modified with sodium silicate is disclosed in Soviet Union Patent 1,033,771. French Patent 2,524,899 discloses a dust control composition which comprises an emulsifiable mineral oil, CMC, a nonionic wetting agent, a plasticizer, water and optionally sodium silicate. The material is used to control dust on unsurfaced roads. U.S. Pat. No. 4,032,352 discloses a binder for mineral ore fines comprising pitch, hydrated lime and/or moist mill scale and sodium silicate in water. The binder is used in forming briquettes of mineral ores. Japanese application (Kokai) 51009103 discloses treatment of peat with sodium silicate to form a colloidal slurry which can be shaped and dried or used as a binder for coal dust.
German Patent 2,401,217 discloses the use of sodium silicate as a binder in the formation of briquettes of SiO.sub.2, Fe.sub.2 O.sub.3, AI.sub.2 O.sub.3, CaO, MgO and C for use in the production of Si. U.S. Pat. No. 3,763,072 discloses a treatment for forming a semi-impervious crust on soil which comprises an aqueous emulsion of a homopolymer of a lower alkyl ester of acrylic acid or of an alpha-lower alkyl acrylic acid or a copolymer of the esters and sodium silicate.